No, the woosh will be less and the whine will be less as rpm goes down. In my tests I have found the fan is much quieter with 3s than 4s in all regimes.

I also think that the fan is not suited to less blades, it already shows a lot of loss at mild changes in outlet area with all the blades present.

Eric B.

By reducing the blade area you will have alower power input rwquired but still can have the RPM there. Now if this doesnt work and i cant get it ballanced then yes i i will leave it stock and run less rpm. If whoosh and whine are way less then still better then a high rpm whine!!

By reducing the blade area you will have alower power input rwquired but still can have the RPM there. Now if this doesnt work and i cant get it ballanced then yes i i will leave it stock and run less rpm. If whoosh and whine are way less then still better then a high rpm whine!!

Yup I understand what your saying, changing aspect ratio of the blade will lighten the load of which this fan doesn't need the aspect ratio changed. It only requires the right kv and motor length to get proper performance. The aspect ratio is already a bit to high which hurts performance under high loading.

Yup I understand what your saying, changing aspect ratio of the blade will lighten the load of which this fan doesn't need the aspect ratio changed. It only requires the right kv and motor length to get proper performance. The aspect ratio is already a bit to high which hurts performance under high loading as when the outlet tube area is reduced less than ~90percent FSA.

Eric B.

Why is this?

Is there some type of cavitation or something that happens at the blades that cause them to lose thrust with less than 90% FSA?

Well something is bothering them under high backpressure. They don't work as well in the same plane you have had a 5 or 6 blade in. Unless it had a nice unrestricted exhaust path to start with.

I have always wondered about this "FSA %" thing (have outlet X % of FSA).... because a different blade area, blade count, blade pitch and blade 'twist' etc must have the potential alter everything a lot, from fan to fan.
5 and 6 blade cheapies seem a roughly same blade design, but Wemo, or 3 or 4 blade.... then CS10 blade.. some other 8 blades.... are covering a very large portion of the fan 'tube', so they must have different effects.
eg 5 and 6 blade typically cover something like 40% of the open area. The CS10 covers 90% or more by the looks.
So the optimal - or even needed - opening FSA % could vary by a LOT from fan type to fan type. Not just 95%... 90%... 85%.... but matter a lot, and be far more critical to some than others too.

There will be no hard and fast rule to apply. Just what has been tested, and shown in numbers, for a given plane and fan etc, to work. Also ALL of the setup matters for that result to apply. Fan, RPM used etc.

So it would seem that having blades in closer proximity to each other muct make for more interactions of airflow, turbulence, between them. And if a fan has more of that fan area 'covered' (by blades), like the CS10, then it has more of a 'solid wall' of air, and thus probably a dislike for backpressure - as it has 'nowhere to go'... no 'thinner' air to compress into, like a lower area blade total fan could cope with.
CS10... 90% static area coverage (a guess).... can't deal with backpressure due to that higher end % number.... must have 90% FSA outlet - or something at least much closer to its static area % coverage, maybe 88% etc. Just 1% variation being quite important to it.
5 blade..... 45% static area coverage (a guess again)..... backpressure still matters, but far less than a CS10..... optimal at 80% FAS (made up number for this fan)..... but can still run fine at 75% to 95% anyway. 5% variation doesn't bother it. It would be far more lenient to a variation and 'absorb' tolerance far easier for little output change.

That all means that a CS10, for any given airframe and motor/RPM setup, would be far more important to have its exhaust path (and propably inlet side too really) quite finely tuned to suit that exact setup you have.
Even the exact same airframe, with one person using a different motor and thus RPM capability, could quite notably alter. Whichever 'fluked' the better tuned result could have big gains over the 'poorer' suited setup.
A thrust number probably doesn't tell you this exactly - but in an end result it could be a measure of use. It is probably more to do with CFM, as the fan needs to be able to get out the CFM for the further coming flow to be unhindered always.

Yeah the video is bad, phone cams seem to screw up the audio a lot. Its actually so quiet you dont hear it in the air, no roar, nothing, its a bit freaky actually, I didnt like it at first because it had no intake or exhaust roar but Rudes loves it. Wait till I get some video on my new cam, so far the sound has been really honest with it. Our weather has been terrible lately, this weekend was another blow out, and I got the flu anyway so barely able to type right now

AGREE WITH ALL OF THE ABOVE! love that jet and yes actually it's freakishly dead silent.the vid's audio is no way near what it actually sounds outhere.i like the 'silent but deadly' side of it

Is there some type of cavitation or something that happens at the blades that cause them to lose thrust with less than 90% FSA?

Would a change of the stator pitch help in any of this?

Regards

erh7771,

I thought I had soemthing that would support my thoughts on this but after I looked back at the posts on the outlet sizes/thrust all I could find were posts that were all over the map from 50% to no outlet on the fan with some data. I will test my own fans on a restrictor setup that Klaus Schornhorst posted several years back and will report back when I get it done.

Also guys i am not tryingto get max power out of these fans, if wanted to do that i would just order a setup from EXT. As i stated earlier these will go in some FREE GWS 262's I have. looking for low power set up with somewhat of a whoosh sound. now if there was a 64mm version it would be simple.

Also guys i am not tryingto get max power out of these fans, if wanted to do that i would just order a setup from EXT. As i stated earlier these will go in some FREE GWS 262's I have. looking for low power set up with somewhat of a whoosh sound. now if there was a 64mm version it would be simple.

Eric, I modified the blades of the Haoye 90mm rotor years ago, cut them down around 20% or so and tried a few different versions, made very little difference to the amp draw, just lost thrust.

Hi Mark,

I think I remember a post on that a few years back. What I remember is the rotor was machined on the back side changing the chord and the pitch?
I think what we see is the reason why Stuart hasn't built a 70mm version of his 100/90/80 series.

Extreme do you sell the fan with stock housing and have extra fan rotors? Also i havent went thru all 300 pages again but is the HK fan the same? like i said looking for a low power set up. I think the stock GWS fans put out around 20 ounces max so around there or more would be good. i know this fan would put out way more than that but might sound good on something like this.